Publication Date:
2017-09-14
Description:
We used paired continuous nitrate (NO 3 - ) measurements along a tidally-affected river receiving wastewater discharge rich in ammonium (NH 4 + ) to quantify rates of change in NO 3 - concentration ( ) and estimate nitrification rates. NO 3 - sensors were deployed 30 km apart in the Sacramento River, California (USA), with the upstream station located immediately above the regional wastewater treatment plant (WWTP). We used a travel-time model to track water transit between the stations and estimated every 15-minutes (October 2013-September 2014). Water temperature was strongly related to changes in NO 3 - concentration. In the presence of wastewater, was generally positive, ranging from about 7 µM d −1 in the summer to near zero in the winter. Numerous periods when the WTTP halted discharge allowed the to be estimated under no-effluent conditions, and revealed that in the absence of effluent net gains in NO 3 - were substantially lower but still positive in the summer and negative (net sink) in the winter. Nitrification rates of effluent derived NH 4 ( R Nitrific_E ) were estimated from the difference between measured in the presence versus absence of effluent, and ranged from 1.5-3.4 µM d −1 , which is within literature values but ten-fold greater than recently reported for this region. R Nitrific_E was generally lower in winter (∼2 µM d −1 ) than summer (∼3 µM d −1 ). This in situ, high frequency approach provides advantages over traditional discrete sampling, incubation, and tracer methods, and allows measurements to be made over broad areas for extended periods of time. Incorporating this approach into environmental monitoring programs will facilitate our ability to protect and manage aquatic systems.
Print ISSN:
0043-1397
Electronic ISSN:
1944-7973
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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